Base frame structure for containers or load carrying platforms

ABSTRACT

The base frame structure for containers or load carrying platforms has an outer rectangular frame structure with longitudinal side beams (13) and transverse beams extending between the side beams. Between the longitudinal side beams and transverse beams is mounted a dished sheet metal underpan, preferably welded to the side beams (13) and transverse beams. Sheet flooring material (4) such as sheet plywood or wooden planks are supported on the underpan and preferably fixed one to the other by adhesive bonding. A space (5) defined between the underpan and flooring material is filled with a rigid load distributing filling material (6) such as polyurethane foam having a high density, 60 Kg/m 3  for example. The underpan is curved in at least two directions to distribute load forces applied to the flooring. The underpan is of a reduced thickness resulting in a lighter base frame structure. The flooring element of underpan (3), flooring (4) and filler (6) can be manufactured separately and is readily installed and removed.

The present invention relates to base frame structure for containers,load carrying platforms, commonly known as flat racks or other likeconstructions which are movable from one transporting device to anotherand for storage purposes.

Conventional base structures of this type generally comprise arectangular frame structure with longitudinal side beams and maintransverse beams extending therebetween. Interspersed between the maintransverse beams are a number of spaced transverse members each having aZ-shaped (or other shape) profile serving to support flooring whichgenerally consists of sheet plywood or wood planks. These additionaltransverse members are closely spaced to ensure that the containerfloors are able to resist both the load of goods located thereon andalso heavy point loads, such as that applied by the wheels of a forklifttruck for example. When containers or flat racks are removed from atransporter and placed upon the ground it is not always easy to ensurethat the ground has a perfectly flat surface and it is possible toposition the container on the ground directly over odd pieces of brick,rubble or metal which can cause severe distortion of the intermediatetransverse members, thus weakening the base flooring structure.

U.K. No. 954539-A discloses a container with a curved bottom portionwhich is part of the integral structure of the container and does notlie between transverse beams.

In U.K. No. 2044728-B there is described a base structure in which theclose spaced Z-shaped (or other shape) profile members are omitted anddownwardly curved sheet metal plates (hereinafter referred to as"underpans") which are curved in one direction and are secured betweenthe main transverse beams below the flooring with the curved edge of thesheet material abutted and welded to respective oppositely disposedlongitudinal frame beams. The usual sheet flooring is located across andis supported by the transverse beams and the space between the flooringpanels and the downwardly curved sheet material is filled with a rigidfilling such as wood chippings and adhesive which distributes the loadapplied to the portion of the floor between the transverse beams to themetal plates. The underpan is less subject to contact with rubble sinceit lies higher in the frame structure and is easy to paint and reducescorrosion.

However, such a construction has been found to be disadvantageous inthat it is very heavy since the thickness of the one-way downwardlycurved sheet material has to be sufficient to support not only the rigidfilling material but also any load which is applied to the flooring.Typically the minimum thickness of the sheet metal underpan is 2 mm.

According to one aspect of the present invention there is provided abaseframe structure for containers or load carrying platformscharacterised in that the dished sheet underpan is curved in at leasttwo directions and that the flooring of sheet material is supported onthe underpan.

Generally, the dished pan is one with sides higher than the major areaof the central portion. The term curved for this disclosure includes across-section in which the sides and base are straight lines angled toeach other to form a general dish shape.

In one preferred embodiment of a base frame structure according to thepresent invention the directions in which the underpan is curved aretransverse to each other, preferably at right angles.

The underpan is preferably formed as a one piece stamping from a singlesheet of metallic material. In another preferred form a single sheet ofmetal is shaped at the corners thereof such that when edge portions ofthe sheet are bent upwardly the shaped edges of one edge portion engageand are welded to the cut edges of the next adjacent edge portions.

Preferably, the extreme outer edge of each edge portion is provided withan outwardly extending flange for connecting the underpan to thetransverse and longitudinal beams of the base frame structure.

Conveniently, sheets of the flooring material are sealingly abuttedtogether and to the underpan. The flooring can be provided with holestherein through which a polyurethane or other rigid foam mixture can bepumped into the space between the underpan and the undersurface of theflooring. Some of the holes in the flooring are provided to allow airand eventually the foam material, when the space is filled to flow fromsaid space, whereupon the foam injection is stopped. The outer flangearound the edge of the sheet material is preferably arranged to contactand be fixed to, the longitudinal and transverse beams for example bywelding. Conveniently the longitudinal side beams are of a generallyC-shaped cross section and the transverse beams have an I-shapedcross-section.

In an alternative construction the longitudinal and transverse beams areof an I-shaped or other shaped cross section and the outer flange aroundthe edge of the sheet metal member is bent downwardly and outwardly forcontact with the upper surface of these members.

The plywood flooring is shaped so as to fit within the dished metalmember with its top surface lying flush with the upper exposed surfaceof the outer flange of the underpan welded to the transverse member andconsequently when installed substantially co-planar with the uppersurface of the transverse beams. The plywood flooring is preferablybonded to the underpan with adhesive, although rivets or nuts and boltscan be provided to secure the plywood to the sheet metal member afterbonding.

According to another aspect of the invention there is provided a floorelement for a container or load carrying platforms locatable betweentransverse beams characterised in a base underpan curved in at least twodirections and being mountable on upper surfaces of the transverse andlongitudinal members of the container, a flooring mounted on and fixedrelative to the periphery of the underpan, and a load distributing rigidfilling material filling the space between the flooring and theunderpan.

To support the underpan at least the transverse container beams can beconfigured to provide a sloped surface between the upper surface and thevertical face, on which angled underpan edge flanges can rest and beattached. The flooring sheeting can be shaped at the periphery on itslower surface to co-operate with the shaping of the periphery of theunderpan.

In a modification the adjacent ends of floor elements could abut on topof the transverse beams, the flooring material within each element beingtherefore co-planar with the flooring material of other elements but notnecessarily with the upper surface of the transverse beams.

A preferred embodiment of a base frame structure according to thepresent invention will now be described by way of example with referenceto the accompanying drawing in which:

FIG. 1 is a plan view of a shaped sheet metal underpan for use in thebase frame structure according to the present invention,

FIG. 2 is a cross sectional view of part of the underpan taken along theline A--A of FIG. 1,

FIG. 3 is a sectional view through a longitudinal side rail or beam andmodified form of underpan structure, and

FIG. 4 is cross sectional view of part of a transverse beam of the baseframe structure with an underpan attached to each side thereof.

Referring more specifically to the drawings, a base frame structureaccording to the present invention comprises two parallel longitudinalside members which are beams or rails 1 and transverse beams 2 tointerconnect the longitudinal side rails at the extreme ends thereof andat selected locations along the length of the side rails.

A downwardly extending dished underpan 3 of sheet material is interposedbetween adjacent transverse beams and longitudinal side rail members. Asheet of plywood or other suitable flooring material 4 sits on theunderpan 3 in the region of the edges thereof to define a space 5between the flooring and the underpan, which space is filled withpolyurethane foam 6, (or other filling material).

The underpan 3 shown in FIG. 1 and FIG. 2 is of a rectangularconfiguration and has a generally flat base portion 10 and outwardly andupwardly sloping portions 11 suitably shaped from a single sheet ofmetal material such as steel, so that when the portions 11 are curvedupwardly the individual sloping portions 11 engage the next adjacentsloping portions along lines 12, whereupon the sloping portions 11 areinterconnected, preferably by welding. An outer flange 13 is providedalong the extreme outer edge of the portions 11 and this flange 13 isarranged to contact the side rails and transverse beams and is welded tothese members so that the underpan 3 is supported on all its four sides.The flange 13 rests on a sloped surface 14 formed at the edge of each ofthe respective longitudinal and transverse beams.

Base portion 10 is of a generally flat configuration whilst the slopedportions 11 slope upwardly with a ratio of 6.25:1. The flanges 13 arearranged to have a different slope of 3.5:1. As previously indicatedeach flange 13 is welded along its free edge and along its underside toa respective one of the side rail 1 and transverse beam 2. A seal andfiller sealant of hard rubber for example is provided along the welds toprotect the same.

The plywood flooring preferably comprises two abutting sheets of plywoodeach having its under surface along the remaining three sides, shaped inthe region of its edges to conform with the sloping of the portions 11of the underpan. The plywood flooring is fixed to the underpan firstlyby bonding with adhesive (not shown) and then, if necessary, by rivetsor other suitable fixing devices. The polyurethane foam 6 which ispumped into the space 5 through holes (not shown) in the wood flooring 4is preferably a high density polyurethane foam having a density of 60Kg/m³. Such a high density foam assists in distributing forces caused bya load applied to the underpan through the flooring. Higher or lowerdensity foam can be used depending on the particular use for which thecontainer or load carrying platform is designed. The pressure of thefoam within the space 5 causes the base portions 10 and 11 to bowslightly.

Generally bonding of the flooring with the underpan assists in thetransfer of tension forces between the shear connections at the junctionof the flooring and underpan. Furthermore, the provision of curving ofthe underpan in transverse directions surprisingly has been found tospread the effect of forces applied thereto and thereby to considerablyto reduce point loading on the underpan. Accordingly, a considerablereduction in thickness of the underpan is possible for a given loadcondition than was possible in the prior art. A reduction of 50% in thethickness of the underpan is possible with a resultant saving in weight.Typically the thickness of the underpan used with the base framestructure of the present invention is 1 mm.

The base frame structure of the present invention is also easy to paintand maintain to reduce corrosion whilst in presenting only a relativelysmall area at its lowermost point, the structure is less likely to besubjected to damage.

Since the underpan rests upon and is welded to the longitudinal andtransverse members it is readily replaceable by cutting out around itsedges. The surfaces of the longitudinal and transverse member are thencleaned and prepared and another underpan flooring unit is locatedwithin the space provided on the container and welded into position.

Therefore, there is provided a flooring unit which is lighter than otherunderpan floorings, is manufactured separately from the container withwhich it is used, and is easily replaceable without having to replacethe whole of the container flooring thus considerably reducing the costof maintenance and repair.

The flooring unit itself is manufactured by shaping a sheet of metal sothat it is curved in two or more directions, placing the underpan on amould to support the underpan, locating preformed sheet flooring membersonto the underpan, sealing the sheet members together and bond themsealingly to the underpan. Rivets or nuts and bolts can be used tocompletely secure bonding of flooring to underpan. Polyurethane foam isthen pumped through holes in the flooring until the foam exudes fromother holes in the flooring whereupon the space between the flooring andunderpan is filled.

The flooring unit is then located on top of the longitudinal andtransverse beams and welded to them. A seal and filler sealant of hardrubber for example is provided along the welds to protect the same.

Referring now to the modified form of the underpan shown in FIGS. 3 and4 the construction is substantially identical to that shown in FIG. 2,however, the outer flange 13 is not sloped but lies parallel to the flatbottom portion 10 to rest upon the rectangularly shaped longitudinalside rail or transverse beam. In this case the edge of the flooring willbe within the inner edge of outer flange. In either case the uppersurface of the flooring is substantially co-planar with the uppersurface of the beam.

FIG. 4 illustrates the connection of two underpans 3 of theconfiguration shown in FIG. 3 to transverse member 2, with one underpanon either side thereof. The attachment is made by welding as describedabove for the previously described embodiment.

Preferably, the depth between the upper surface of the sheet flooring 4and the underpan is 40 mm with the plywood being 20 mm thick and thefoam 20 mm thick. The sheet metal of the underpan is 1 mm thick, and isof muffler grade stainless steel.

The underpan is preferably of an elongate rectangular configurationbeing 2430 mm by 2489 mm. The flanges 13 are typically 27 mm wide whilstthe sloping portions 11 are 250 mm wide. However, the underpan can be ofany shape in which the bowing thereof is in two or more directions.

At least two of the transverse members or beams preferably take the formof an inverted generally rectangular U-shape or hollow box configurationwhich extend to the outside of the base frame for receiving the tinesof, for example, a fort lift truck.

Whilst the foam filling has been described as having a density of 60Kg/m³, foam having a density of 100 Kg/m³ or higher can be used.

I claim:
 1. A flooring element for a container or load carrying platformcharacterised by an underpan curved in at least two directions, flooringmeans mounted on and fixed relative to the underpan with space definedtherebetween, and polyurethane foam mixture having a density of at least60 kg/m³ located in and filling the said space between the flooringmeans and underpan, the flooring element being locatable on andattachable to the longitudinal and transverse beams of a base frame ofthe container.
 2. An element as claimed in claim 1, characterised inthat the sheet material flooring comprises sheets of plywood and isbonded to the underpan with adhesive.
 3. An element as claimed in claim2, characterised in that the sheet material flooring is chamfered on itsunder surface along its outer edges to lie on sloping surfaces of theouter edge portions of the dished underpan so that the top surface ofthe sheet flooring material is flush with the uppermost surface of theouter flange of the underpan.
 4. A base frame structure for containersor load carrying platforms comprising a longitudinal frame structurehaving longitudinal side beams with transverse beams extendingtherebetween and a dished sheet underpan supported on the longitudinaland transverse beams of the base frame structure, a flooring of sheetmaterial and a load distributing rigid filling material located in thespace between the underpan and the under surface of the flooringmaterial, characterised in that the sheet underpan is curved in at leasttwo directions, that the flooring of sheet material is supported on theunderpan, and that the load distributing rigid filling material is apolyurethane foam mixture, having a density of at least 60 kg/m³.
 5. Abase frame structure for containers or load carrying platformscomprising a longitudinal frame structure having longitudinal side beamswith transverse beams extending therebetween and a dished sheet underpan supported on the longitudinal and transverse beams of the base framestructure, a flooring of sheet material and a load distributing rigidfilling material located in the space between the underpan and the undersurface of the flooring material, characterised in that the sheetunderpan is curved in at least two directions and that the flooring ofsheet material is supported on the underpan, the underpan is a singlesheet of metal of rectangular configuration and has edge portions of thesheet bent upwardly, opposite ends of each edge portion engagingrespective ends of the next adjacent edge portions, and in that a flangeextends outwardly from the extreme outer edge of each edge portion forconnecting the underpan to transverse and longitudinal beams of the baseframe structure, at least one pair of opposed flanges being arranged torest on sloped portions of either the longitudinal or transverse beams.6. A structure as claimed in claim 5, characterised in that the sheetmaterial flooring is chamfered on its under surface along its outeredges to lie on sloping surfaces of the outer edge portions of thedished underpan so that the top surface of the sheet flooring materialis flush with the uppermost surface of the outer flange of the underpan.7. A structure as claimed in claim 6, characterised in that the sheetmaterial flooring is bonded to the underpan with adhesive.